1. Field of Invention
This invention relates to gravity-driven car racing, specifically a pendulum-based start gate for race tracks such as used in the popular Pinewood Derby race.
2. Prior Art
Literally millions of Pinewood Derby races have been run since the inception of the race in 1953, mostly by Cub Scouts and their parents. But the currently available race tracks, without exception, have a serious problem in their car start mechanisms. Refer to the prior art FIG. 1 which points out a typical spring-loaded start mechanism, a version of which is shared by all prior art tracks. FIG. 2 shows a typical location of the start gate at the top of an initial elevated track portion called a ramp. The spring force is supplied by strong rubber bands in some designs such as the original Cub Leader How-To Book design. In other designs the spring force is from a torsional hinge-type spring as in the Derby Magic design. But the spring force supplied to move the start posts is about 16 times stronger than necessary, and when the start gate is triggered the start post support structure must undergo a rapid deceleration or “slap” against the ramp bottom to stop its rotation. This “slap” deceleration occurs over a distance on the order of 30 times shorter than necessary. The above combined effects of a large spring force and short deceleration time cause the net deceleration force to be several hundred times more than actually needed. This “slap”, even if damped with a cushion, still causes substantial vibration and impact motion of the ramp which jostles the cars, such as 20, thereby interfering with a smooth, fair start. The inherent performance capability of a car and the true winner will thus be masked by the above problem found in prior art start gates. More detail regarding gate “slap” will be provided in the Mechanical Theory section.
To further explain this problem, refer again to prior art FIG. 1, where we see that the items associated with the start gate are mounted on a plate 18 or on other ramp members such as a main support stand 17 or even the side of the ramp 19 itself. A plurality of start posts such as 22 are supported by some rigid member such as a wooden or metal bar 23 which is mounted to the ramp underside by a hinge with pivot 24. Upon release of the bar 23 the spring 26 causes the bar 23 to rapidly rotate around the hinge pivot 24 according to the motion arrows until the bar slaps with considerable force against the underside of the ramp. Whenever the bar 23 rotates, a lever 28 in the start switch assembly 27 causes a start signal to be sent to a race timer.
The references listed on the attached Information Disclosure Form are examples of prior art:    1) The Cub Scout Leader “How-To Book” is the oldest known start gate activation method. It teaches a start gate powered by a heavy rubber band.    2) The Micro Wizard web site teaches a spring-loaded start gate using two linear springs.    3) The Derby Magic web site teaches a spring-loaded start gate using a torsion-type spring.